Toggle Main Menu Toggle Search

Open Access padlockePrints

The NANOGrav 15 yr Data Set: Harmonic Analysis of the Pulsar Angular Correlations

Lookup NU author(s): Dr Anne ArchibaldORCiD

Downloads

Licence

This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).

Abstract

© 2025. The Author(s). Published by the American Astronomical Society.Pulsar timing array observations have found evidence for an isotropic gravitational-wave background with the Hellings-Downs angular correlations between pulsar pairs. This interpretation hinges on the measured shape of the angular correlations, which is predominantly quadrupolar under general relativity. Here we explore a more flexible parameterization: we expand the angular correlations into a sum of Legendre polynomials and use a Bayesian analysis to constrain their coefficients with the 15 yr pulsar timing data set collected by the North American Nanohertz Observatory for Gravitational Waves (NANOGrav). When including Legendre polynomials with multipoles ℓ ≥ 2, we only find a significant signal in the quadrupole with an amplitude consistent with general relativity and nonzero at the ∼95% confidence level and a Bayes factor of 200. When we include multipoles ℓ ≤ 1, the Bayes factor evidence for quadrupole correlations decreases by more than an order of magnitude due to evidence for a monopolar signal at approximately 4 nHz, which has also been noted in previous analyses of the NANOGrav 15 yr data. Further work needs to be done in order to better characterize the properties of this monopolar signal and its effect on the evidence for quadrupolar angular correlations.

Publication metadata

Author(s): Agazie G, Anumarlapudi A, Archibald AM, Arzoumanian Z, Baier JG, Baker PT, Becsy B, Blecha L, Boddy KK, Brazier A, Brook PR, Burke-Spolaor S, Burnette R, Casey-Clyde JA, Charisi M, Chatterjee S, Cohen T, Cordes JM, Cornish NJ, Crawford F, Cromartie HT, Crowter K, DeCesar ME, Demorest PB, Deng H, Dey L, Dolch T, Ferrara EC, Fiore W, Fonseca E, Freedman GE, Gardiner EC, Garver-Daniels N, Gentile PA, Gersbach KA, Glaser J, Good DC, Gultekin K, Hazboun JS, Jennings RJ, Johnson AD, Jones ML, Kaplan DL, Kelley LZ, Kerr M, Key JS, Laal N, Lam MT, Lamb WG, Larsen B, Lazio TJW, Lewandowska N, Liu T, Lorimer DR, Luo J, Lynch RS, Ma C-P, Madison DR, McEwen A, McKee JW, McLaughlin MA, McMann N, Meyers BW, Meyers PM, Mingarelli CMF, Mitridate A, Nay J, Ng C, Nice DJ, Ocker SK, Olum KD, Pennucci TT, Perera BBP, Petrov P, Pol NS, Radovan HA, Ransom SM, Ray PS, Runnoe JC, Saffer A, Sardesai SC, Schmiedekamp A, Schmiedekamp C, Schmitz K, Shapiro-Albert BJ, Siemens X, Simon J, Siwek MS, Smith TL, Fiscella SVS, Stairs IH, Stinebring DR, Stovall K, Susobhanan A, Swiggum JK, Taylor J, Taylor SR, Turner JE, Unal C, Vallisneri M, van Haasteren R, Vigeland SJ, Wahl HM, Witt CA, Wright D, Young O

Publication type: Article

Publication status: Published

Journal: Astrophysical Journal

Year: 2025

Volume: 985

Issue: 1

Print publication date: 20/05/2025

Online publication date: 16/05/2025

Acceptance date: 03/04/2025

Date deposited: 23/06/2025

ISSN (print): 0004-637X

ISSN (electronic): 1538-4357

Publisher: Institute of Physics

URL: https://doi.org/10.3847/1538-4357/adc997

DOI: 10.3847/1538-4357/adc997

Altmetrics

Altmetrics provided by Altmetric

Funding

Funder referenceFunder name
Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555
BGU (Kreitman fellowship)
CIFAR
Larry W. Martin and Joyce B. O’Neill Endowed Fellowship in the College of Science at Oregon State University
n NSF CAREER award #2146016
NASA through the NASA Hubble Fellow- ship Program grant #HST-HF2-51453.001
NASA under award No. 80GSFC21M0002
NSF AccelNet award No. 2114721, an NSERC Discovery Grant
NSF operated under cooperative agreement (AST-1744119)
NSF under award #181566
NSF under award 1847938
NSF #1458952
NSF #2009425
NSF AST-2007993
NSF Astronomy and Astrophysics grant (AAG) award No. 200946
NSF Astronomy and Astrophysics Postdoctoral Fellowship under award AST-2202388
NSF award PHY-2011772
NSF grant No. 2207267
Sloan Fellowship
The David Dunlap family and the University of Toronto
The National Science Foundation Graduate Research Fellowship under grant No. DGE-2139292
The Research Corporation for Science Advancement under Cottrell Scholar Award No. 27553
The Science and Technology Facilities Council, grant NoST/W000946/1
The Simons Foundation
UBC Four Year Fellowship (6456)
the Caltech and Jet Propulsion Laboratory President’s and Director’s Research and Development Fund
The Council for Higher Education and the Israel Academy of Sciences and Humanities (Excellence fellowship)
The Deutsche Forschungs- gemeinschaft under Germany’s Excellence Strategy—EXC 2121 Quantum Universe—390833306
The Eötvös Loránd Research Network (ELKH)
The George and Hannah Bolinger Memorial Fund in the College of Science at Oregon State UniversitY
The Gordon and Betty Moore Foundation
The Grote Reber Fellowship Program administered by Associated Universities, The Astrophysical Journal, 985:99 (12pp), 2025 May 20 Agazie et al. Inc./National Radio Astronomy Observatory
The National Aeronautics and Space Administration (80NM0018D0004)
The National Science Foundation (NSF) Physics Frontier Center award Nos. 1430284 and 2020265
The National Science Foundation Graduate Research Fellowship under grant No. DGE-174530
The National Science Foundation under award AST-1909933
The National Science Foundation under grants No. NSF PHY-1748958 and AST-2106552
The Naval Research Laboratory by NASA under contract S-15633
Vanderbilt Initiative in Data Intensive Astrophysics (VIDA) Fellowship

Share